Martina Mosing1, Ulrike Auer2, Paul MacFarlane3, David Bardell4, Johannes P Schramel2, Stephan H Böhm5, Regula Bettschart-Wolfensberger6, Andreas D Waldmann5. 1. Section of Anaesthesiology, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland; College of Veterinary Medicine, Murdoch University, Perth, Australia. Electronic address: m.mosing@murdoch.edu.au. 2. Veterinary University Vienna, Vienna, Austria. 3. Langford Veterinary Services, University of Bristol, Bristol, UK. 4. School of Veterinary Clinical Science, University of Liverpool, Neston, UK. 5. Swisstom AG, Landquart, Switzerland. 6. Section of Anaesthesiology, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland.
Abstract
OBJECTIVE: The aim of this study was to evaluate the effect of continuous positive airway pressure (CPAP) on regional distribution of ventilation and dead space in anaesthetized horses. STUDY DESIGN: Randomized, experimental, crossover study. ANIMALS: A total of eight healthy adult horses. METHODS: Horses were anaesthetized twice with isoflurane in 50% oxygen and medetomidine as continuous infusion in dorsal recumbency, and administered in random order either CPAP (8 cmH2O) or NO CPAP for 3 hours. Electrical impedance tomography (and volumetric capnography (VCap) measurements were performed every 30 minutes. Lung regions with little ventilation [dependent silent spaces (DSSs) and nondependent silent spaces (NSSs)], centre of ventilation (CoV) and dead space variables, as well as venous admixture were calculated. Statistical analysis was performed using multivariate analysis of variance and Pearson correlation. RESULTS: Data from six horses were statistically analysed. In CPAP, the CoV shifted to dependent parts of the lungs (p < 0.001) and DSSs were significantly smaller (p < 0.001), while no difference was seen in NSSs. Venous admixture was significantly correlated with DSS with the treatment time taken as covariate (p < 0.0001; r = 0.65). No differences were found for any VCap parameters. CONCLUSIONS AND CLINICAL RELEVANCE: In dorsally recumbent anaesthetized horses, CPAP of 8 cmH2O results in redistribution of ventilation towards the dependent lung regions, thereby improving ventilation-perfusion matching. This improvement was not associated with an increase in dead space indicative for a lack in distension of the airways or impairment of alveolar perfusion.
OBJECTIVE: The aim of this study was to evaluate the effect of continuous positive airway pressure (CPAP) on regional distribution of ventilation and dead space in anaesthetized horses. STUDY DESIGN: Randomized, experimental, crossover study. ANIMALS: A total of eight healthy adult horses. METHODS:Horses were anaesthetized twice with isoflurane in 50% oxygen and medetomidine as continuous infusion in dorsal recumbency, and administered in random order either CPAP (8 cmH2O) or NO CPAP for 3 hours. Electrical impedance tomography (and volumetric capnography (VCap) measurements were performed every 30 minutes. Lung regions with little ventilation [dependent silent spaces (DSSs) and nondependent silent spaces (NSSs)], centre of ventilation (CoV) and dead space variables, as well as venous admixture were calculated. Statistical analysis was performed using multivariate analysis of variance and Pearson correlation. RESULTS: Data from six horses were statistically analysed. In CPAP, the CoV shifted to dependent parts of the lungs (p < 0.001) and DSSs were significantly smaller (p < 0.001), while no difference was seen in NSSs. Venous admixture was significantly correlated with DSS with the treatment time taken as covariate (p < 0.0001; r = 0.65). No differences were found for any VCap parameters. CONCLUSIONS AND CLINICAL RELEVANCE: In dorsally recumbent anaesthetized horses, CPAP of 8 cmH2O results in redistribution of ventilation towards the dependent lung regions, thereby improving ventilation-perfusion matching. This improvement was not associated with an increase in dead space indicative for a lack in distension of the airways or impairment of alveolar perfusion.
Authors: Olivia A Brabant; David P Byrne; Muriel Sacks; Fernando Moreno Martinez; Anthea L Raisis; Joaquin B Araos; Andreas D Waldmann; Johannes P Schramel; Aline Ambrosio; Giselle Hosgood; Christina Braun; Ulrike Auer; Ulrike Bleul; Nicolas Herteman; Cristy J Secombe; Angelika Schoster; Joao Soares; Shannon Beazley; Carolina Meira; Andy Adler; Martina Mosing Journal: Front Vet Sci Date: 2022-07-22
Authors: Martina Mosing; Stephan H Böhm; Anthea Rasis; Giselle Hoosgood; Ulrike Auer; Gerardo Tusman; Regula Bettschart-Wolfensberger; Johannes P Schramel Journal: Front Vet Sci Date: 2018-03-28